Pedicle screw for intervertebral support elements

ABSTRACT

The pedicle screw ( 1 ) for intervertebral support elements ( 3 ) consists of a shaft ( 10 ) and a head ( 2 ) comprising at least two parts ( 20, 22 ). The head is formed as a securing means for at least one support element ( 3 ). Each support element consists of a piece of a cable-like band ( 31 ) and a cylindrical support body ( 30 ) with an axial lumen ( 31″ containing the band. The band is securable outside end surfaces ( 32 ) of the support body in the head. The head is formed with a contact surface ( 23 ) via which a pressure stress can be exerted on the support body in the band direction, and indeed using the band and in cooperation with a further pedicle screw. A part ( 20 ) of the head ( 2 ), which is firmly connected to the shaft ( 10 ) at the one end of the latter, contains a base groove ( 21 ) which is oriented transversally to the shaft and into which the part of the band ( 31 ) to be secured or a connecting piece ( 292 ) which contains the band can be introduced during the securing of the support element ( 3 ) by means of a translatory movement in the direction of the shaft and fixed there.

[0001] The invention relates to a pedicle screw for intervertebralsupport elements in accordance with the preamble of claim 1.

[0002] Invasive treatment methods are known for the stabilization ofspinal columns in which bone bridges are made to grow between adjacentvertebral bodies using implants. Stiffening fusions of the adjacentvertebrae result through the bone bridges. In addition to stiffeningoperations of this kind a treatment method for stabilizing by means ofan implant system is also known in which no fusion arises, but rather amobility is preserved between adjacent vertebrae. This implant systemcomprises pedicle screws and intervertebral support elements which areimplanted during the operation from the back. Each pedicle screw has ahead which is formed as a ring. In each case two pedicle screws arescrewed in in a vertebral body through the pedicle passages of thevertebra. The support elements are secured at the screw heads. Twosupport elements which are arranged in parallel between adjacentvertebrae form a dynamic supporting of these vertebrae. Thevertebrae—with the exception of the lowermost lumbar vertebra—can ineach case also be connected at the same pedicle screws to an upwardlyand a downwardly adjacent vertebra through two pairs of supportelements.

[0003] Each support element consists of a piece of a cable-like band anda cylindrical support body which is elastically yielding. A rigidmaterial can also be used for individual support bodies in order tostiffen the spinal column at individual locations. The band is drawn inin an axial lumen of the support body. The intervertebral supportelements are secured at the pedicle screws using the band. In this thebands must be drawn through through the ring heads. The drawing in ofthe band is an operation step which is difficult to carry out.

[0004] The object of the present invention is to create, for dynamicvertebra supporting, a pedicle screw for intervertebral support elementsfor which the securing of the support element at the pedicle screw,which must take place during the surgical operation, can be carried outmore easily. This object is satisfied by the pedicle screw which ischaracterized in claim 1.

[0005] The pedicle screw for intervertebral support elements consists ofa shaft and a head which comprises at least two parts. The head isformed as a securing means for at least one support element. Eachsupport element consists of a piece of a cable-like band and acylindrical support body with an axial lumen which contains the band.The band can be secured outside end surfaces of the support body in thehead. The head is formed with a contact surface via which a pressurestress can be exerted on the support body in the band direction, andindeed using the band and in cooperation with a further pedicle screw. Apart of the head, which is firmly connected to the shaft at the one endof the latter, contains a base groove which is oriented transversally tothe shaft and into which the part of the band to be secured or aconnecting piece which contains the band can be introduced during thesecuring of the support element by means of a translatory movement inthe direction of the shaft and fixed there.

[0006] Subordinate claims 2 to 11 relate to further advantageousembodiments of the pedicle screw in accordance with the invention.

[0007] The invention will be explained in the following in more detailwith reference to the drawings. Shown are:

[0008]FIG. 1 a lumbar vertebra showing the position of two pediclescrews,

[0009]FIG. 2 two pedicle screws with an intervertebral support elementfor two adjacent vertebrae,

[0010]FIG. 3 an outline illustration of adjacent lumbar vertebraeshowing the position of two implanted support elements,

[0011]FIG. 4 the head of a pedicle screw in accordance with theinvention together with a support element,

[0012]FIG. 5 a second embodiment of the head with a T-shapedgroove-stone,

[0013]FIGS. 6, 7 two heads in which disc-shaped parts are arrangedbetween the support element and the head,

[0014]FIG. 8 a head with a connector,

[0015]FIG. 9 a variant of the connector of FIG. 8,

[0016]FIG. 10 a head with a sleeve part

[0017]FIG. 11 a further embodiment of the head with a connector and

[0018]FIG. 12 a cross-section through the head of the embodiment inaccordance with FIG. 10.

[0019] A lumbar vertebra 9 in accordance with FIG. 1 consists of avertebral hole 90, a vertebral body 91 and a vertebral arch 92 whichcomprises two pedicles 93, two transverse processes 94, a spine 95 of avertebra and articular processes 96. The positions of two pedicle screws1 in the implanted state are indicated in chain-dotted lines. In thesepositions the heads 2 of the pedicle screws 1 are located directly atthe outer side of the pedicles 93 between the transverse processes 94and the articular processes 96. FIG. 2 shows two pedicle screws 1, whichare provided for two adjacent vertebrae 9 and between the heads 2 ofwhich, which are formed as rings, an intervertebral support element 3 isarranged. Shafts 10 of the pedicle screws 1 are screwed in into thevertebrae 9. The heads 2 have notches 4 laterally which are required forthe implanting and orientation of the pedicle screws 1 by means of aninstrument. The support element 3 consists of a piece of a cable-likeband 31 and a cylindrical support body 30 in which the band 31 iscontained in an axial lumen 31′. The band 31 is secured outside of endsurfaces 32 of the support body 30 in each case in the heads 2 of thepedicle screws 1 with a setting screw 22. The heads 2 are provided withplanar contact surfaces 23 via which a pressure stress can be exerted onthe support body 30 in the band direction via their end surfaces 32,with the tension force required for this being produced using the band31 and in cooperation with the pedicle screw 1 of the adjacent vertebra9.

[0020] An outline drawing with two adjacent lumbar vertebrae 9 is shownin FIG. 3. The positions of two implanted support elements 3 areindicated.

[0021] The pedicle screw 1 in accordance with the invention differs fromthe known pedicle screw through a specially formed head 2. The supportelement 3 can be laid in into the latter by means of a translationalmovement in the direction of the shaft 2, so that the support element 3can be fixed in the head without a drawing in of the band 31 into aneye-like securing means being required.

[0022] A first embodiment of the head 2 of a pedicle screw 1 inaccordance with the invention is illustrated in FIG. 4 together with asupport element 3. A part 20 of the head 2 which comprises two lugs 20 aand 20 b and which is firmly connected to the shaft 10 contains a basegroove 21 which is oriented transversely to the shaft 10 and a thread24. A part of the band 31 which is to be secured is inserted into thebase groove 21 during the securing of the support element 3 and is fixedwith a screw 22. The base groove 21 has a shape which corresponds to theshape of the band in such a manner that the base groove is formedcomplementarily in the insertion region. An edge region 21′ of the basegroove 21 can—in order to prevent a damage to the inserted band 31—beformed in such a manner that the base groove 21 widens in the directiontowards the contact surface 23.

[0023] The embodiment of FIG. 4 is a first example of a pedicle screw inaccordance with the invention, in which the lugs 20 a, 20 b, which formflanks of the base groove 21, have depressions 24 on their inner sidesinto which a securing part, namely the screw 22, can be firmly anchoredby means of a form lock. After the production of the form lock the lugs20 a, 20 b are advantageously elastically spread apart somewhat by thesecuring part 22, so that the position of the latter is additionallyfixed as a result of an increased adhesive friction and thus of a forcelock.

[0024] A second example is shown in FIG. 5, in which the lugs 20 a, 20 bhave groove-like depressions 24 a on their inner sides. A T-shapedgroovestone 25 with lateral ribs 25 a is pushed in between the grooves24 a after the insertion of the band 31—cf. FIG. 5—and for fixing theband 31 a setting screw 22—cf. FIG. 5—is screwed into a bore in thegroove-stone 25 with inner thread 250.

[0025]FIGS. 6 and 7 show in each case a head 2 in which a disc-shapedpart 26 is arranged between the support element 3 and the head 2. Thehead 2 in FIG. 6 comprises a core part 20 and at least one disc-shapedpart 26 which forms the contact surface 23 to the cylindrical supportbody 30 of the support element 3 on the one side and which forms acontact surface 261 to the core part 20 on the other side. The surfaceof the core part 20 is made spherical. The contact surface 261 to thecore part 20 of the disc-shaped part 26 is made in the shape of aspherical section corresponding to the shape of the core part 20. Thedisc-shaped part 26 is applied together with the support body 30 to theband 31, with the band 31 being drawn into the bore 260. This drawing inof the band 31 is carried out prior to the implanting of the supportelement 3 outside the body of the patient to be operated on.

[0026] The head 2 in FIG. 7 comprises a core part 20 which has at eachend of the groove 21 an elevation 262 which is formed to fitcomplementarily to a groove 263 of the disc-shaped part 26 (ridge-grooveform lock). The groove 263 can be pushed onto the elevation 262 in thedirection of the—shaft 10. As was already the case in the example ofFIG. 6, the part 26 is applied to the band 31 prior to the implanting.

[0027]FIG. 8 shows a head 2 with a core part 20 and with a connector 27which is a sleeve-like part and the inner space of which has a squareprofile which is formed by planar surfaces. The core part 20 is tightlyenclosed by the connector 27, so that a spreading open of the lugs 20 a,20 b during the screwing in of a screw 22 (see FIG. 10) into the thread24 is prevented.

[0028]FIG. 9 shows a variant 27′ of the connector 27 of FIG. 8. Thisconnector 27′ is made longer in the direction of the groove 21 or of thebore 270 and contains a bore with inner thread 272. The band 31 canadditionally be fixed below the threaded bore 272 with a second screw22.

[0029]FIG. 10 shows a head 2 with a sleeve part 28 and with a core part20 which is firmly connected to the one end of the shaft 10. Thescrew-cap part 28 is displaceable along the entire shaft 10 up to thenamed shaft end. In this the thread 24 comes to lie over the groove 21so that the screw for the securing of the band 31 can be screwed intothe thread 24.

[0030]FIG. 11 shows a further embodiment of the head 2 with a connector29. The band 31 can be secured in the connector 29 in a bore 293. Duringthe operation the connector 29, which contains the band 31, is placedonto the core part 20 of the head 2, with a connecting piece 292 of theconnector 29, which has a prismatic shape, being laid in into thecorresponding complementarily shaped groove 21. The securing between theconnector 29 and the core part 20 can be produced for example with twoscrews. The non-illustrated screws are inserted through bores 291 a ofthe connector 29 and are screwed tight in threaded bores 291 b of thecore part 20.

[0031] The embodiments in accordance with FIGS. 6 and 10 permit aso-called “polyaxiality” in the fixing of the support body 30 at thepedicle screws 1. The “polyaxiality” relates to the axis of the shaft 2;in all other body 30, which is given by the axis of their lumens 31′.The term “polyaxiality” is intended to mean that the angle between thetwo axis directions is not fixed in advance, but can vary within acertain angular range. This will be explained for the embodiment inaccordance with FIG. 10 in more detail with reference to FIG. 12: FIG.12 shows a cross-sectional illustration of the pedicle screw head 20with the sleeve part 28, the inner surface 280 of which is a partialregion of a spherical surface. The head 20 is made correspondinglyspherical, so that it can be laid in into the sleeve part 28 indifferent positions. The axis of the shaft 10 has a main direction zperpendicular to the direction x of the support body 30 (x isperpendicular to the plane of the drawing). The shaft axis can deviatewith respect to this main direction z by an angle (φ. This angle φ has amaximum value φ_(max) which amounts to 10° or even more, but which isless than 15°. The angle φ can vary in the region of a cone about themain direction z, with the half opening angle of this cone amounting toφ_(max). Corresponding remarks also hold for the embodiment inaccordance with FIG. 6. The system for the vertebral support which canbe produced with the pedicle screws in accordance with FIGS. 6 and 10 iseasier to implant thanks to the “polyaxiality”.

[0032] Longitudinal components comprising support elements are anchoredin vertebrae with pedicle screws, with a dynamic stabilizing of thevertebrae being producible thanks to an elastic yielding of the supportelements. The pedicle screws in accordance with the invention permit ahead feeding of the longitudinal components. In the head feeding thelongitudinal components are laid in into the heads of the pedicle screwsin that merely a translational movement in the direction of the shaft inthat merely a translational movement in the direction of the shaft needbe carried out. Through a simple insertion of this kind the operationtechnique is obviously substantially simplified with respect to theolder treatment methods, in which the bands of the support elements mustbe drawn in into the screw heads, which are formed in ring shape.

1. Pedicle screw (1) for intervertebral support elements (3), consistingof a shaft (10) and a head (2) which comprises at least two parts (20,22), with the head being formed as a securing means for at least onesupport element (3), with each support element consisting of a piece ofa cable-like band (31) and a cylindrical support body (30) with an axiallumen (31′) which contains the band, with the band being securableoutside end surfaces (32) of the support body in the head and with thehead being formed with a contact surface (23) via which a pressurestress can be exerted on the support body in the band direction, namelyusing the band and in cooperation with a further pedicle screw,characterized in that a part (20) of the head (2), which is firmlyconnected to the shaft (10) at the one end of the latter, contains abase groove (21) which is oriented transversally to the shaft and intowhich the part of the band (31) to be secured or a connecting piece(292) which contains the band can be introduced during the securing ofthe support element (3) by means of a translatory movement in thedirection of the shaft and fixed there.
 2. Pedicle screw in accordancewith claim 1, characterized in that the band (31) can be fixed in thehead (2) with a screw (22), in particular with a cylindrical screw. 3.Pedicle screw in accordance with claim 1 or claim 2, characterized inthat the base groove (21) has a shape which corresponds to the shape ofthe band (31) or to that of the connecting piece (292) which containsthe band respectively in such a manner that the base groove is formedcomplementarily in the insertion region.
 4. Pedicle screw in accordancewith any one of the claims 1 to 3, characterized in that the base groove(21) is arranged between two lugs (20 a, 20 b) in their base region; andin that the lugs have on their inner side thread-like or groove-likedepressions (24; 24 a) into which a securing part (22; 25), inparticular a screw (22), can be anchored by means of a form lock, withthe lugs advantageously being elastically spread apart somewhat by thesecuring part after the production of the form lock so that the positionof the securing part is additionally fixed as a result of a force lock.5. Pedicle screw in accordance with claim 4, characterized in that thesecuring part is a platelet (25) which can be inserted into grooves (24a) at the crowns of the lugs (20 a, 20 b) parallel to the base groove(21); and in that it contains a bore with inner thread (250) into whicha screw (22) can be screwed in for fixing the band (31).
 6. Pediclescrew in accordance with any one of the claims 1 to 4, characterized inthat the head (2) comprises a core part (20) and at least onedisc-shaped part (26); and in that the disc-shaped part forms thecontact surface (23) to the cylindrical support body of the supportelement on the one side, whereas it forms a contact surface (261) to thecore part on the other side; or in that the head (2) comprises a corepart (20) and a sleeve-like part (27) which tightly encloses the corepart.
 7. Pedicle screw in accordance with claim 6, characterized in thatthe surface of the core part (20) is formed spherically; and in that thecontact surface (261) which the disc-shaped part (26) has to the corepart is formed in the shape of a spherical section corresponding to theshape of the core part.
 8. Pedicle screw in accordance with claim 6,characterized in that the disc-shaped part (26) can be connected to thecore part (20) via a ridge-groove form lock (262, 263); and in that theridge (262) and the groove (263) respectively are oriented in thedirection of the shaft (10).
 9. Pedicle screw in accordance with any oneof the claims 1 to 4, characterized in that a part of the head (2) is asleeve part (28) for a core part (20) of the head, with the core partbeing the part (20) which is firmly connected to the one shaft end andthe sleeve part being displaceable along the entire shaft (10) up to thenamed shaft end.
 10. Pedicle screw in accordance with any one of theclaims 1 to 4, characterized in that band (31) can be secured in aconnector (29); and in that the connector can be secured on a core part(20) of the head, with the core part being the part (20) which is firmlyconnected to the one shaft end.
 11. Pedicle screw in accordance withclaim 7 or claim 9, characterized in that the axis of the shaft (10) hasa main direction (z) which extends perpendicularly to the direction (x)of the support body or support bodies (30); and in that the shaft axiscan deviate with respect to this main direction by an angle (φ) which isless than 150.